As VCRs (Video Cassette Recorders) have been coming into wide use, it has become possible to easily view video data of recorded television broadcast or contents of software which can be reproduced by the VCR. In addition, recently, digital VCRs and recording/reproduction apparatus for DVDs (Digital Video Discs) have been progressed, whereby high-quality video data can be recorded and reproduced. Since the high-quality video data can be easily recorded/reproduced because of the recent progress in the VCRs and the DVD recording/reproduction apparatus, the security of copyrights on video data which are recorded on the digital VCRs or DVDs has become important. Therefore, various methods for preventing unauthorized copying have been conventionally carried out.
For example as for analog video signals, there is a method by which copying is protected with utilizing a difference in AGC (Auto Gain Control) methods between the VCR and the TV, or a difference in characteristics of APC (Auto Phase Control).
However, in the conventional copy protection method, only a carrier signal which is obtained by modulation of a color signal can be protected against copying, while a color-difference signal which is not modulated cannot be protected against copying. More specifically, for a color-difference signal which is not modulated as shown in FIG. 15 or a component video signal which is composed of primary-color signals, there is no suitable copy protection method and thus these signals can be easily copied.
The present invention is made in view of the above-mentioned problems and has for its object to provide a copy protection method for a component signal which is composed of a luminance signal and color-difference signals, and a digital broadcast receiver for outputting the copy-protected component signal.